Chemistry: (This won't add the slightest bit of help or info about
PD, just a little fun to share with the technically minded.) From
time to time I wondered about the loose and interchangeable use of
the terms DOPA, L-DOPA, Levodopa, and Dopamine- so I decided to look
up the definitions. The books don't all agree exactly, but I think I
have a handle on it that is adequate for my degree of interest.
Names of compounds are often chosen to tell a little about the
chemcal's composition. DOPA is an acronym, or shorthand, for
DihydrOxyPhenylAlanine, as depicted below. The diagrams are another
kind of shorthand, where chemists can recognize familiar groups and
see how they go together. You need to recall from freshman chemistry
how compound molecules are made of atoms connected by something
called valence bonds, of which each element has a characteristic
number: Hydrogen 1, Oxygen 2, Nitrogen (usually) 3, and Carbon 4.
In DOPA, the hydroxyl group is water, H2O, minus a hydrogen. The
phenyl is based on the benzene hexagon, C6H6, and Alanine, itself
an amino acid when complete, is the group on the right. DOPA
becomes Dopamine when the C-O-OH part of the alanine group is
replaced by a single hydrogen atom. Levodopa refers to the fact that
the DOPA molecule isn't flat like its diagram, but has a three=
dimensional aspect that permits more than one shape. When you look
at a solution of DOPA through a Polaroid filter, you find that one
of its forms twists the polarization to the left, or "levo". The
Different forms of a compound may have identical composition but
quite distinct chemical properties. The best analog I can think of
for right- or left-handedness is in a pair of dice. If you obey the
convention that marks on opposite sides of each cube must add up to
7, and look at a corner so you can see 1, 2, and 3, there are two
possible arrangements: clockwise and counterclockwise. Something
like that happens in many chemical compounds.
H H H H
| | | /
H C H H---C---C---N---H
\ // \ / | |
C C H C--O--H
| || \\
C C O
/ \\ / \
H C H Alanine
|
H
Benzene
H H
| |
H--O C H H H H--O C H H H
\ // \ | | / \ // \ | | /
C C---C---C---N--H C C---C---C---N--H
| || | | | || | |
C C H C--O--H C C H H
/ \\ / \ \\ / \\ / \
H--O C H O H--O C H
(Dihydroxy) | (Alanine) |
H H
(Phenyl) (Carboxyl)
DOPA = DihydrOxyPhenylAlanine Dopamine
(Levodopa)
J. R. Bruman (818) 789-3694
3527 Cody Road
Sherman Oaks CA 91403
